Petroleos Mexicanos, the state oil monopoly, is heavily taxed to finance the government's budget and is starved for cash to develop the country's abundant natural gas reserves. So Mexico now imports, at high prices, close to 20 percent of the natural gas it uses. All of that comes from the United States.

"We are importing from an importer," said Dionisio Perez-Jacome, president of Mexico's Energy Regulatory Commission, the federal regulator for private energy investment. "It's always better to be at the beginning of the chain rather than at the end." The government estimates that demand for natural gas will grow 6.8 percent a year through 2012. Much of that is driven by rising electricity use, because natural gas is needed to fuel new power plants.

LNG, or liquefied natural gas, is gas supercooled to a liquid state that takes up one-six hundredth of the space it does at room temperature, allowing it to be transported by tanker to terminals close to markets. There, it can be revaporized and piped to homes and industry. Building liquefied natural gas terminals, Perez- Jacome said, would enable Mexico to import gas from more distant sources, like South America, Russia and Indonesia, and end Mexico's dependence on U.S. imports.

Permit applications for three LNG terminals are moving through Mexico's federal and state bureaucracies. Two terminals would be in the state of Baja California, which covers the northern part of the peninsula. The third, the project that is furthest along, is at Altamira, a large industrial port on the Gulf of Mexico.

Opposition has focused on the proposals for Baja California, a region where environmental awareness has increased sharply in the last decade, with critics raising the environmental and safety concerns that recently shelved similar projects in California, Maine and Alabama.

Many opponents also say that the real purpose of the Baja California projects is to supply natural gas to California, putting Mexican communities at the mercy of insatiable U.S. energy needs.

In the first Baja California project, divisions of Royal Dutch/ Shell Group and Sempra Energy, a company based in San Diego, are planning a $600 million project about 80 kilometers, or 50 miles, south of the U.S.-Mexico border and need only a few permits to begin construction in the next few months, said Daniel Fobelets, manager of the joint venture for Shell. The terminal would supply 28 million cubic meters, or one billion cubic feet, of natural gas a day, almost three times what the state of Baja California consumes now, once the terminal is completed in 2007. Half will be exported to the United States.

The second proposal, from ChevronTexaco, calls for a $650 million offshore terminal on a platform almost 13 kilometers, or eight miles, off the coast of Tijuana and an eighth of a kilometer from the pristine South Coronado Island. If the permits are granted, construction would begin next year, said Carlos Atallah, vice president of ChevronTexaco de Mexico.

The terminal would begin by processing nearly 20 million cubic meters of natural gas a day in 2007, with 70 percent of the total for Mexico and the remainder for California. Referring to an accident this year in Algeria that killed more than 20 people, opponents argue that liquefied natural gas terminals are unsafe. They also say the proposed Baja California terminals threaten an already strained coastal environment. But what most infuriates opponents are the export plans. "The problem with these projects is that the gas is for the California market," said Arturo Moreno, climate and energy campaign coordinator for Greenpeace Mexico.

The natural gas, he said, also could be used in the future to fuel power plants to provide electricity to the United States, as two plants on the border at Mexicali already do. One, operated by Sempra, sells all its power to the United States. The second, built by InterGen, a joint venture between Shell and Bechtel, sends half its electricity north.

Energy companies talk about an integrated market, Moreno said, but "there is a double standard for environmental impact."

"We have more corrupt institutions," he said. "We have more lax environmental standards and much worse enforcement." Perez-Jacome, the regulator, said that Mexican environmental and safety standards are "top of the line." And executives on both projects say they are sensitive to environmental concerns.

"The reason we went though the trouble to permit such a complex project is because we are convinced that this is the best project with the smallest impact," said Atallah of ChevronTexaco.

"It is important to be able to export gas to the United States because that will stabilize the price in Mexico as well," he said. "The more gas you put in the system, the better for everyone."

But industry executives acknowledge that not all the proposals will succeed and that community opposition already scuttled one proposal.

In March, Marathon Oil of Houston backed out of a plan to build a $1.7 billion energy complex south of Tijuana after the Baja California state government expropriated part of the site.

Sergio Tagliapietra, the state's economic development secretary, said the government had acted to resolve ownership disputes, but he acknowledged that opposition from residents of Playas de Tijuana, a nearby well-to-do suburb of Tijuana, had influenced his decision- making.

Environmental groups and federal and state legislators opposed to the ChevronTexaco project say the Coronado Islands support a diverse seabird colony and are home to California sea lions and harbor seals.

"We are surprised that Chevron had the nerve to propose the project," said Alfonso Aguirre, director of a local nongovernmental organization, Conservacion de Islas, which is looking at legal options to block it.

"They thought of this option because they could not build in an inhabited area."